CN111194248A

CN111194248A - Electromagnetic pulse coil with replaceable conductor

Info

Publication number: CN111194248A
Application number: CN201880062554.0A
Authority: CN
Inventors: 巴勃罗·帕斯奎尔
Original assignee: Piester Products Co Ltd
Current assignee: Piester Products Co Ltd
Priority date: 2017-09-26
Filing date: 2018-09-07
Publication date: 2020-05-22
Also published as: PT3651930T; RU2741440C1; DK3651930T3; PL3651930T3; CA3074871A1; KR20200057719A; ES2896690T3; US20210339335A1; JP2023037010A; EP3651930A1; JP7334371B2; DE102017122229A1; LT3651930T; DE112018005513A5; HUE056189T2; JP2020535020A; EP3651930B1; JP7220220B2; WO2019063038A1; US11090757B2

Abstract

An electromagnetic pulse welding coil is disclosed, comprising two regions, a first region having a higher current density than a second region, the first region being detachably connected to the second region when the coil is used. A method of increasing the useful life of the coil by replacing areas with higher current densities is also disclosed.

Description

Electromagnetic pulse coil with replaceable conductor

Technical Field

The present invention relates to an electromagnetic pulse welded coil comprising a high current density region and a remainder of the coil having at least one low current density region, and a method for extending the life of such a coil.

Background

Electromagnetic pulse forming/welding is a forming and/or welding process for metal workpieces, in which strong time-varying magnetic fields induce high eddy currents in the workpiece to be machined at the desired location to be formed, wherein high forces are exerted on the region of the workpiece to be formed due to the coupling of the eddy currents with these induced fields. This force is directed away from the power generation source according to the well-known lenz's law. Its strength is proportional, on the one hand, to the field strength of the induced magnetic field and, on the other hand, to the change of this field strength over time.

In the prior art, it is known to generate a magnetic field for shaping by means of a planar coil having two mutually adjacent windings which are excited by a time-varying, usually sinusoidal, current. In order to achieve the desired high field strength on the one hand and to obtain a clearly defined shaped region on the other hand, the coils are shaped such that they comprise at least one narrow bridge which, when connected in series with a region of wide cross section, causes a concentration of the current and thus a high current density in the region of the bridge. Such coils are hereinafter referred to throughout as "pulse-welded coils", although they are generally equally applicable to pure forming of workpieces. The field strength of the resulting shaped magnetic field and its change over time is directly proportional to the current density, and thus the force acting on the workpiece is proportional to the square of the current density amplitude. Accordingly, in the design of pulse welding coils, efforts are made to use bridges that are as narrow as possible.

However, conversely, there are the following facts: due to the high current density and thermal stress, and due to the forces acting on the coil from the workpiece, the material of the coil is also subjected to high mechanical stresses, which leads to rapid fatigue of the region loaded with the high current density, that is to say, the generally narrow bridge. This disadvantageously limits the life of such pulse welding coils.

This problem has long been recognized in the prior art and solutions have been attempted by various means. For example, japanese published application JP2004-342535a discloses a pulse-welded coil in which a coil loaded with a high current density is embedded in a non-conductive structure that mechanically supports it and can also be cooled by active cooling. However, pulse welding coils designed in this way are very thick compared to the generally preferred planar pulse welding coils and are also complicated to produce and operate. The former because mechanical support structures of non-conductive material must be formed around the actual pulse welding coils, and the latter because active cooling systems, including cooling fluid channels and circulation pumps, must be provided, connected, filled, and particularly maintained.

Published application JP2010/110814a proposes placing a known pulse welding coil with a narrow coil bridge symmetrically disposed between low current density regions between the two sides of two machined workpieces. In this way, the forces applied by the workpiece to the coil or coil bridge, respectively, partially cancel each other out and mechanical loads or even bending or coil bridge are avoided or at least reduced. However, this cannot always be carried out, such as, for example, in the case where there is only a single workpiece to be treated, or in the case where a particular orientation of the workpiece to be formed or of two workpieces to be connected to one another is to be maintained.

The specification of the applicant's european patent EP2670554B1 describes a planar pulse welded coil in which the gap between a narrow cross-section coil bridge loaded with a high current density and a coil component of relatively low current density having a larger cross-section is filled with a cooling insulator. Thereby, an electrical insulator is meant, however, it has a high thermal conductivity. Materials having such characteristics are, for example, boron nitride or aluminum nitride. With this design it is advantageously achieved that heat generated in the region loaded with high current density is dissipated through the highly thermally conductive material in the remaining part of the coil. Furthermore, a mechanical connection is created between the coil bridge and the rest of the coil, so that the latter cannot be bent by reaction forces from the workpiece. In contrast to the above-described solution with active cooling, the planar design of the coil can still be maintained.

In a separate application, it is possible to use a pulse welded coil to simultaneously machine two workpieces, however, it has become apparent from the above example that it is generally not a solution to the problem of mechanical stress of narrow coil bridges. The solution proposed by the above patent specification is preferred for this purpose, however with the following disadvantages: with a cooling insulator, difficult to handle materials must be inserted into the pulse welding coil, which increases manufacturing costs and time. Although the lifetime is extended to a higher degree than the manufacturing costs, there is still a need for a pulse welding coil which can have a planar design and which is simple and cost-effective to manufacture and which still achieves a long effective lifetime.

Disclosure of Invention

Against this background, it is an object of the present invention to provide such a pulse welding coil.

This object is achieved by an electromagnetic pulse welding coil, wherein a region loaded with a high current density, such as a coil bridge, is detachably connected to the remainder of the coil. In this way, when material fatigue or even material fracture occurs, the high stress areas can be replaced and the remainder of the coil can continue to be used, which is consistent with the significantly lower load combined with the more size dependent spring back, typically having a lifetime many times longer than the high current density areas.

According to the invention, there is at least one replaceable, that is to say detachably connected, region which is subjected to a high current density. However, in a pulse welding coil including a plurality of such regions, it is entirely possible to design all the regions so that they are replaceable by detachable connections.

In the case of a double-winding coil, it comprises two regions of the coil having a large cross-section and a relatively low current density, which is generally U-shaped and symmetrical. In the symmetry plane of the coil, a narrow coil bridge is provided which concentrates the current during the welding current pulse and in this way achieves a high current density, and thus a high field strength, at least segment by segment. The invention now proposes to make the coil bridge replaceable by connecting it to the rest of the coil in a removable manner. For this purpose, on the one hand, the use of a connection method is considered, and on the other hand, detachable fastening by other methods is also considered.

The former includes fixing, for example by means of screws or bolts which are introduced into recesses or holes provided for this purpose, firstly in the region or coil bridge loaded with the high current density and secondly in the remaining part of the coil, and are fixed on the opposite side by means of a locking nut. Tightening the nut with the maximum possible torque ensures a surface contact between the conductive surfaces of the coil bridge and the rest of the coil, which is very important to avoid parasitic resistances at the high currents used in pulse welding.

As an alternative to the union nut, the thread of the screw or bolt can also engage with a threaded hole introduced into the remaining part of the coil or the coil bridge, the screw or bolt being first guided through the part of the coil bridge or the remaining part of the coil which is not provided with an internal thread and then screwed into the other part which is provided with an internal thread. Here, as with the use of self-locking nuts, care must be taken to ensure as close a fit as possible in order to establish the face contact.

Alternatively or in combination with the use of screws or bolts, the components loaded with high current density, in particular the coil bridge and the rest of the coil, can also be detachably connected by plugging together. In order to achieve the greatest possible surface contact, the invention proposes that the remaining part of the coil be provided with a recess or depression complementary to the first end region of the coil bridge, which recess or depression can extend over a substantial part of the length of the coil bridge.

The recess or depression can also have a cross section which tapers in the insertion direction of the coil bridge and, in combination with the cross section of the first end of the coil bridge (which also tapers in the wedge shape towards the end), leads to a better frictional connection and a greater surface contact of the two components with one another. Especially if the recess is designed as a continuous opening in the remaining part of the coil, the coil fabric is inserted into this opening from one side and, after complete introduction, emerges again on the other side. In this case, the fastening can be effected by means of fastening pins or bolts, which, if they are also designed in the form of wedges, lead to an increase in the contact pressure. Similarly, by using clamping pliers, the tension of the bridge can be influenced.

Besides the prior art single winding coil as described above comprising two passive components, which are generally symmetrical with low current density, and a narrow coil bridge in a symmetrical fashion in the coil, other designs are also conceivable which can also benefit from the principles proposed by the present invention. Such an embodiment is a double-winding coil comprising two mirror-symmetrical sub-coils, each of which comprises an area with a large lateral extension (that is to say width) and a corresponding low current density, and a coil bridge parallel to the first area, which has a small lateral extension or width and a corresponding high current density. The two sub-coils are arranged such that their coil bridges are parallel at a small distance from each other and are electrically connected in series, the two sub-coils being connected to a pulsed current generator, wherein it should be noted that the currents in the two coil bridges flow in the same direction.

The complete system has the advantage that the coil bridge cross section can be further reduced and the current density can be correspondingly further increased compared to a single-winding coil. Furthermore, in the case where the workpiece is disposed above the coil bridges at a small distance, the region having the highest eddy current density is also subjected to acceleration due to the distance between the coil bridges, and the region having the highest eddy current density is more sharply restricted than in the case of a single-winding coil. In this way, it is possible to achieve that the workpiece to be deformed or welded to the interface element is machined in a well-defined area, which is feasible in comparison with a single winding coil. By varying the distance between the two sub-coils, the width of the region to be deformed or welded can also be varied to some extent. According to the invention, the coil fabric of each sub-coil is detachably connected to the remaining part of the sub-coil, for example by one of the ways described above.

The main advantages of the electromagnetic pulse welding coil according to the invention are obviously the following facts: the areas of highest current density are replaceable, these areas are generally the most fatiguing during operation and contribute to the short life of the pulse welded coil. It is thus advantageously avoided that the coil as a whole needs to be replaced and can be reused, even if the remaining part of the coil has only a lower current density and accordingly a much longer life than the coil bridge. With a loop fabric, only relatively small parts, which are easy to manufacture, need to be updated, which saves material and costs. Furthermore, the replacement of the coil bridges can also be carried out significantly faster than the replacement of the entire coil, so that, for example, after fatigue fracture of the coil bridges, production is only stopped for a shorter time than in the case of conventional coils.

Advantageous embodiments of the invention, which can be implemented individually or in combination, are described in more detail below.

The pulse welding coil according to the invention is planar in design, for example the cutting of metal sheets. The high current density region can preferably be designed as a narrow bridge, which particularly preferably comprises a widened end region with which the narrow bridge is detachably connected to the remainder of the coil. This increases the contact surface area which firstly facilitates the transfer of current from the remaining part of the coil into the coil bridge, in particular reduces the parasitic ohmic resistance, and secondly also improves the loss of mechanical load from the coil fabric into the remaining part of the coil.

In order to detachably connect a region which is loaded with a high current density, in particular a coil bridge, the invention proposes to connect this region to the remainder of the coil by means of a screw connection or plug connection.

Threaded connections by screws or bolts can be produced in that they are guided through aligned openings or holes in the coil fabric and the rest of the coil and are fixed with locking nuts on the opposite side. It is also conceivable to provide the coil bridge, the remaining part of the coil or both with a threaded hole in which a screw or bolt is tightened. For this solution, it is preferable to screw the thread into the coil bridge, since when the coil bridge is replaced, the thread is also replaced, which may be damaged by screwing and reopening the bolt.

It is also conceivable to introduce a threaded hole into the remainder of the coil, into which a bolt inserted through the hole of the bridge is screwed. This solution offers the advantage that the bolt can be introduced from above when replacing the coil bridge, and that the bridge can be placed on the rest of the coil.

For fixing the coil bridge, preferably more than one screw is used.

Alternatively, it is preferable to insert the region loaded with high current density, in particular the coil bridge, into a recess complementary thereto or into a continuous opening of the remaining part of the coil. It is particularly preferred that the coil bridge is fixed on the side opposite to the insertion side by means of fixing pins or wedges in order to prevent accidental extraction or falling off, and that the coil bridge is connected with a high contact pressure in the remaining part of the coil by means of the use of fixing wedges in combination with a cross section of the coil bridge that tapers in the shape of a wedge and an opening in the remaining part of the coil that accommodates the coil bridge.

To further reduce the parasitic ohmic resistance at the connection point between the high current density replaceable region and the remainder of the coil, a conductive patch or other means for increasing the effective contact surface area may be inserted.

The coil according to the invention may be mirror symmetric. Preferably, the remaining part of the coil is designed as a U-shaped metal part with a substantially rectangular cross section, the width of which at all points exceeds a few times, preferably 3-1000 times, the width of the cross section of the region loaded with the high current density.

Another preferred embodiment is a pulse welded coil where only L-shaped areas of low current density are present, the high current density areas being detachably connected to the short legs at their end areas and extending parallel and adjacent to the long legs.

In order to further increase the life of the coil according to the invention, it is proposed to design the cross section of the remaining part of the coil (that is to say the low current density region) and the cross section of the coupling region with the high current density region or of the coupling region of the coil bridge, and to design the coil bridge such that the cross section changes continuously in the contour of the coil. It is particularly preferred that the cross section is changed in a continuously differentiable manner (continuously differentiable manager). This means that in the contour of the coil there is preferably no abrupt change in the size of the cross-sectional area and particularly preferably also no bending. Possible and particularly preferred embodiments thus comprise the provision that all inner corners of the remaining part of the coil and all inner corners of the coil bridge are designed to be circular, the radius of curvature preferably corresponding approximately to the width of the coil bridge.

It is proposed to extend the life of an electromagnetic pulse welded coil according to the invention with a replaceable coil bridge in the electromagnetic pulse welded coil, for example if the coil bridge breaks, or at least deforms or fatigues significantly, it is detached and removed from the rest of the coil and a newly provided, usually identical, coil bridge is connected again to the rest of the coil. In particular those areas of the coil which are affected by high current densities are subject to high wear. This applies in particular to coil bridges. After such a rapid change of the coil bridge, the coil can continue to operate.

Drawings

Further details and features of the invention will be described in more detail below with reference to the drawings of exemplary embodiments. These examples are intended to illustrate the invention only and do not limit the generality of the invention.

Wherein:

fig. 1 shows a three-sided view of a first preferred embodiment of a pulse welding coil according to the present invention.

Fig. 2 shows the replacement of the coil bridge of the embodiment of fig. 1.

Fig. 3 shows a preferred embodiment of a pulse-welded coil according to the invention with an L-shaped region of low current density, wherein the coil bridge is fixed by a plug connection.

Fig. 4 shows the mounting of a coil bridge in the embodiment of a coil according to the invention shown in fig. 3.

Detailed Description

Fig. 1 shows in three views a preferred embodiment of a pulse-welded coil according to the invention having a U-shaped region of low current density to which, in one plane of symmetry of the coil, a coil bridge having a dumbbell-shaped profile is detachably fixed at one of its two ends by means of a bolt.

In the top view shown in partial view B, the replaceable coil bridge 11 has a double mirror-symmetrical dumbbell-shaped profile, the coil bridge 11 having an elongated central portion 111 and wider end plates 112. In each end plate 112, two holes 110 are introduced in each case. The remaining part 19 of the coil, which part 19 comprises two parts 12 which extend parallel to the coil bridge and are loaded with a low current density, has a mirror-symmetrically designed U-shaped profile. At each end of the U-shaped leg, and at the apex of the inner region, a pair of holes 120 is introduced, in each case mirror-symmetrically with respect to the plane of symmetry S.

The coil bridge 11 is detachably connected to the remaining part 19 of the coil by arranging the end plate 112 on the apex region of the U-shaped inner region so that the hole 110 of the coil bridge 11 is aligned with the threaded hole 120 of the remaining part 19 of the coil, inserting a bolt through the hole 110 from above and screwing into the threaded hole 120. In this way, a pulse-welded coil is obtained with two legs of large cross section and a coil bridge of small cross section, which is centrally and symmetrically arranged. A hole 110 introduced in an end plate 112 facing away from the fixed end serves to fix the bridge to the source of the pulsed current, and a hole 120 is in the end region of the leg of the remaining part 19 of the coil. As can be seen in the side views in the partial figures B and C, the coil bridge is mounted on the remaining part of the coil and is therefore attached thereto vertically offset.

It is also conceivable to introduce a stepped recess complementary to the end plate 112 into the apex region of the passive component 119, so that the coil bridge lies substantially in the same plane as the rest of the coil. This has the advantage that the overall coil has a low structural height, but this is associated with a high production outlay for passive components, and also reduces the height of the threaded bore, whereby such a high fastening force of the bolt or screw to which the coil bridge 11 and the remaining part 19 of the coil are connected is no longer possible.

The process of changing the coil bridge is shown in fig. 2. Partial view a shows a pulse welded coil according to the invention with a replaceable coil bridge 11, which is replaced due to material fatigue as shown. For this purpose, the bolts 20 are loosened and the coil bridge 11 is removed (partial view B).

A new coil bridge 11' is provided and placed with the end plate 112 on the apex region of the U-shaped remainder 19 of the coil so that the holes 110 are aligned with the threaded holes 120, as indicated by the arrow in the partial view B, which is directed towards the remainder 19 of the coil. The bolt 20 is then inserted through the hole 110 in the threaded hole 120 and tightened. The replacement is thus completed and the coil according to the invention can be used for further welding or forming of the work piece (partial view C).

Fig. 3 shows another preferred embodiment of the pulse welding coil of the present invention. It comprises a low current density L-shaped area 19 with a continuous recess 190, said continuous recess 190 being located on the shorter leg and tapering locally from one end to the other, into which continuous recess 190 the loop fabric 11 is inserted, and at one end area of the loop fabric 11 an end area 115, which end area 115 is complementary to the recess 119 and also tapers in a wedge shape. The end of the bridge 11 opposite the tapered end region 115 includes an end plate 112 having a continuous aperture 110 therein. An opening 113 is provided at an end 115 of the bridge 11 inserted into the recess 190, and a fixing wedge 30 is inserted through the opening 113 to fix the bridge 11 against accidental sliding or falling off. However, the fixation wedge 30 also serves to increase the contact pressure and thereby increase the surface contact of the region 115 with the inner wall of the opening 190. The inner angle of the L-shaped area of the transition between the narrow central part 111 and the end plate 112 and the transition between the central part and the area 114 are rounded with a radius of curvature corresponding to about 10% of the length of the coil bridge and approximately the width of the coil bridge.

Fig. 4 shows a perspective view of how the coil bridge 11 of the embodiment of fig. 3 is inserted into a complementary opening 190 in the short leg of the L-shaped remaining part 19 of the coil. In detail a, it is shown how the coil bridge 11 with the region 115 is introduced into the opening such that the end region 115 completely engages through the opening 190. To secure the bridge 11, the securing element 30 is inserted by the end projecting from the other side of the element 19 into the opening 113, after which the final state shown in partial view B is reached.

List of reference numerals

1 pulse welding coil

11 high current density region, coil bridge

110 holes

111 bridge, narrow center

112 widened end region

115 end region

12 low current density region

120 holes, screw holes

19 remaining part of the coil

190 recess of coil bridge

20 bolt

30 fixed wedge block

Claims

1. An electromagnetic pulse welding coil comprising:

-a region (11) with a high current density, and

-a remaining part (19) of the coil having at least one area (12) of low current density,

it is characterized in that the preparation method is characterized in that,

the region of high current density (11) is detachably connected to the remainder of the coil (19).

2. A pulse welded coil according to claim 1, characterized in that the coil is planar in design, in particular cut out of sheet metal.

3. A pulse welding coil according to claim 1 or 2, characterized in that said areas of high current density (11) are shaped as elongated bridges having a transverse extension which is narrow compared to a longitudinal extension.

4. A pulse welding coil according to claim 3, characterized in that the region of high current density (11) designed as a bridge comprises a widened end region by means of which the region of high current density (11) is connected with the remainder (19) of the coil.

5. A pulse welding coil according to any preceding claim, wherein said detachable connection is achieved by:

-a screw or bolt is inserted into an unthreaded hole in the region of high current density (11) and the remaining part of the coil (19) and tightened by a counter nut, or screwed into a threaded hole formed in the region of high current density (11) or the remaining part of the coil (19), and/or

-a plug, in particular by inserting the high current density region (11) with an end region (115) into a complementary recess (190) of the remaining part (19) of the coil, the complementary recess (190) being designed for making a surface contact between two components.

6. A pulse welding coil according to any preceding claim, characterized in that the U-shaped profile of the remaining portion (19) of the coil has a lateral extension generally greater than the transverse extension of the region (11) of high current density.

7. A pulse welding coil according to any preceding claim, wherein the coils are mirror images.

8. A pulse welding coil according to any of the preceding claims, characterized by more than one region (11) of high current density.

9. A pulse welded coil according to any preceding claim, wherein the cross-section of the coil varies continuously, in particular continuously differentiably, over its profile.

10. A method for extending the life of an electromagnetic pulse welding coil of any of claims 1 to 9,

a) releasing the connection of the region of high current density (11) to the remainder of the coil (19) and removing the region of high current density;

b) a new region (11') of high current density is provided and connected to the remainder of the coil (11').